JP4929684B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and in particular, applies a voltage of a predetermined polarity from a contact member to a transfer residual toner remaining on an image carrier after transferring a toner image to charge the transfer residual toner to a predetermined polarity. The present invention relates to an image forming apparatus that adsorbs and collects charged transfer residual toner.

  Conventionally, an image forming apparatus that forms an image using an electrophotographic system such as a laser printer or a digital copying machine is known. In this type of image forming apparatus, generally, a photosensitive member having a uniformly charged peripheral surface is driven to circulate, and a light beam is irradiated on the peripheral surface of the photosensitive member to form an electrostatic latent image. A toner image developed by attaching toner to the latent image is transferred to a recording medium to form an image.

  By the way, in this type of image forming apparatus, not all toner is transferred from the photoconductor to the recording medium, and there may be generated transfer residual toner remaining on the photoconductor, and this transfer residual toner is collected. Various cleaning devices have been proposed.

For example, in Patent Document 1 and Patent Document 2, a voltage having a polarity opposite to the charging polarity of the toner is applied to remove the toner adhering to the traveling charged dielectric (corresponding to the above-described photoreceptor). And a conductive rotating brush that contacts the traveling dielectric, and is disposed in contact with the dielectric surface on the upstream side of the traveling dielectric as viewed from the rotating brush, and is used for discharging the dielectric or charging the dielectric. And a conductive fixing brush to which a voltage having a polarity for converting the voltage to a reverse polarity is applied.
JP-A-63-223681 Japanese Unexamined Patent Publication No. 63-223682

  However, in the cleaning devices disclosed in Patent Document 1 and Patent Document 2, transfer residual toner gradually accumulates on the fixed brush as the usage time elapses, and the deposited transfer residual toner is deposited on the photoreceptor. In particular, when the photosensitive member starts to rotate, a large amount of transfer residual toner is discharged from the fixed brush onto the photosensitive member. There was a problem that defects might occur.

  As a countermeasure against this, it is conceivable to increase the voltage value applied to the rotating brush to increase the suction force between the rotating brush and the transfer residual toner, and to prevent the occurrence of defective cleaning by adsorbing the transfer residual toner to the rotating brush. . However, when the voltage value applied to the rotating brush is increased, the potential difference between the rotating brush and the photosensitive member is increased and discharge is generated, and the discharge generates discharge products such as ozone and NOx. As a result, there arises a new problem that the image formed in the high temperature and high humidity environment may be deteriorated in quality such as white spots.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of preventing the occurrence of defective cleaning while suppressing deterioration in the quality of an image to be formed. .

In order to achieve the above object, according to the first aspect of the present invention, an image carrier having a uniformly charged peripheral surface is driven to circulate, and a light beam is applied to the peripheral surface of the image carrier to thereby generate an electrostatic latent image. An image forming apparatus for forming an image and transferring a developed toner image by attaching toner to the electrostatic latent image onto a recording medium, wherein the image carrier is located downstream in the circumferential direction from the transfer position of the toner image. A contact member that is disposed in contact with the peripheral surface of the image bearing member and is applied with a voltage of a predetermined polarity, and charges the transfer residual toner remaining on the peripheral surface of the image carrier after the transfer to the predetermined polarity; and the contact A voltage that is disposed in contact with the circumferential surface of the image carrier downstream of the member in the circumferential direction and that has a polarity opposite to the predetermined polarity and a predetermined potential difference with respect to the potential of the circumferential surface of the image carrier. The transfer residual toner applied and charged to the predetermined polarity is absorbed. And residual toner recovery means for to collected, deposited on the contact member with the lapse of use time, the transfer residual toner discharged from the contact member on the image bearing member at the time of driving to rotate the start of the image bearing member However, since the rotation of the image carrier, the residual toner collecting means is rotated at least once a predetermined number of times depending on the amount of the transferred residual toner discharged from the start of the circumferential driving of the image carrier. until passing through the voltage controlled potential difference between the peripheral surface and the residual toner collecting means of said image bearing member to control the voltage applied to the residual toner collecting means to be larger than the predetermined potential difference Means.

  According to the first aspect of the present invention, the toner image is transferred by the contact member that is arranged in contact with the peripheral surface of the image carrier downstream of the transfer direction of the toner image and to which a voltage having a predetermined polarity is applied. The transfer residual toner remaining on the peripheral surface of the subsequent image carrier is charged with a predetermined polarity, and is disposed in contact with the peripheral surface of the image carrier downstream in the circumferential direction from the contact member, and the periphery of the image carrier. The residual toner charged to a predetermined polarity is adsorbed and collected by the residual toner collecting means to which a voltage having a polarity opposite to the predetermined polarity with respect to the surface potential is applied.

According to the present invention, the voltage control means causes the transfer residual toner to be at least one or more times determined in advance according to the amount of the transfer residual toner discharged from the start of the circumferential driving of the image carrier . Until the toner passes through the residual toner collecting means as the image carrier rotates, the residual toner collecting means is arranged so that the potential difference between the peripheral surface of the image carrier and the residual toner collecting means becomes larger than a predetermined potential difference. The applied voltage is controlled.

Thus, according to the first aspect of the present invention, the transfer residual toner remaining on the peripheral surface of the image carrier after the transfer is charged to a predetermined polarity, and the transfer residual toner is driven around the image carrier. The circumference of the image carrier is from the start until it passes through the residual toner collecting means along with the rotation of the image carrier at least a predetermined number of times according to the amount of transferred residual toner discharged. Since the potential difference between the surface and the residual toner collecting unit is larger than a predetermined potential difference , at least once determined in advance according to the amount of the transferred residual toner discharged from the start of the circumferential driving of the image carrier. The amount of residual toner that is attracted by the residual toner collecting means increases until the residual toner collecting means passes through the remaining number of times as the image carrier rotates , so that even a large amount of residual toner can be collected. Can Further, a period to increase the potential difference for you are between the periods, it is possible to reduce the occurrence of discharge products. Therefore, according to the present invention, it is possible to prevent the occurrence of defective cleaning while suppressing deterioration in the quality of the formed image.

Incidentally, the invention of claim 1, wherein, as in the invention according to claim 2, wherein said voltage control means, the transfer residual toner, from the time of driving to rotate the start of the image carrier, the amount of the discharged residual toner Accordingly, the voltage value of the voltage applied to the contact member is controlled to increase until it passes through the residual toner collecting means as the image carrier rotates by at least a predetermined number of times. May be. According to a first aspect of the present invention, as in the third aspect of the present invention, the voltage control means is configured such that the transfer residual toner is adjusted to an amount of the transfer residual toner discharged from the start of the circular driving of the image carrier. Accordingly, a potential difference between the peripheral surface of the image carrier and the residual toner collecting means until the toner passes through the residual toner collecting means as the image carrier rotates by a predetermined number of times. Is controlled so as to be larger than the predetermined potential difference, and the voltage value of the voltage applied to the contact member is larger than the voltage of the predetermined polarity. The voltage applied to the contact member may be controlled.

According to a first aspect of the present invention, as in the fourth aspect of the present invention, the contact member is connected to a grounded wiring so that the potential is set to the ground level so that the peripheral surface of the image carrier is removed. and neutralization to a predetermined potential level, said residual toner recovery means, the AC voltage potential difference from the center is a predetermined potential difference is applied about said predetermined potential level, said voltage control means, the transfer residual toner The image carrier passes through the residual toner collecting means with the rotation of the image carrier at least once, which is determined in advance according to the amount of transferred residual toner discharged, from the start of the circumferential drive of the image carrier. Until the voltage difference from the center of the AC voltage applied to the residual toner collecting means is larger than the predetermined potential difference. It may be.

  As described above, according to the present invention, the transfer residual toner remaining on the peripheral surface of the image carrier after the transfer is charged to a predetermined polarity, and for a predetermined period from the start of the circumferential driving of the image carrier. Since the potential difference between the peripheral surface of the image carrier and the residual toner collecting means is larger than a predetermined potential difference, it is possible to prevent the occurrence of cleaning failure while suppressing the deterioration of the quality of the formed image. It has the excellent effect of being able to.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, specific numerical values may be given for convenience of explanation, but the present invention is of course not limited to these numerical values.

[First Embodiment]
FIG. 1 shows a color laser printer 10 (hereinafter referred to as a printer) which is an example of an image forming apparatus according to an embodiment of the present invention. The printer 10 includes image forming units 12Y, 12M, 12C, and 12K that respectively form toner images of colors of yellow (Y), magenta (M), cyan (C), and black (K). A so-called tandem type full-color laser printer in which units 12Y, 12M, 12C, and 12K are arranged in parallel facing the intermediate transfer belt 14, and the toner images of four colors are superimposed while the intermediate transfer belt 14 makes one round. It is.

  The printer 10 includes a paper feed tray 16 at the bottom. A paper feed roll 18 is in contact with the leading end of the paper P set in the paper feed tray 16 in the transport direction, and the paper P is fed one sheet at a time by the paper feed roll 18 and a paper handling means (not shown). Paper is fed from the tray 16 to the downstream side in the transport direction. A pair of transport rolls 20 is arranged on the downstream side of the paper feed roll 18 in the transport direction, and the paper P is transported to the upper transfer unit 22 by the transport force from the transport roll 20.

  The transfer unit 22 is provided with a belt conveyance roll 24A around which the intermediate transfer belt 14 is wound, and a transfer roll 26 pressed against the belt conveyance roll 24A. The intermediate transfer belt 14 is sandwiched between the nip portion of the belt conveyance roll 24A and the transfer roll 26, and the toner image is transferred from the intermediate transfer belt 14 when the paper P passes through the nip portion.

  A fixing unit 28 is disposed downstream of the transfer unit 22 in the conveyance direction. The fixing unit 28 is provided with a heat roll 28A that becomes high temperature and a backup roll 28B that is pressed against the heat roll 28A, and the paper P passes through the nip portion between the heat roll 28A and the backup roll 28B. At this time, the toner is melted and solidified, fixed on the paper P, and discharged out of the apparatus.

  Here, the printing unit 11 in which the image forming units 12Y, 12M, 12C, and 12K superimpose the toner images on the intermediate transfer belt 14 will be described. Note that when distinguishing each color of yellow, magenta, cyan, and black, Y, M, C, and K are added after the code. However, if there is no need to distinguish each color, Y, M, C, and K are omitted.

  The intermediate transfer belt 14 includes the belt conveyance roll 24A described above, a belt conveyance roll 24B disposed on the left side of the belt conveyance roll 24A, and a belt conveyance roll 24C disposed obliquely below the belt conveyance roll 24A. , Is wrapped around. Image forming units 12Y, 12M, 12C, and 12K are sequentially arranged on the surface of the intermediate transfer belt 14 between the belt conveyance roll 24A and the belt conveyance roll 24B so as to face each other along the circumferential direction of the intermediate transfer belt 14. Thus, the toner images of the respective colors formed by the respective image forming units 12 are transferred so as to be superimposed on the intermediate transfer body belt 14.

  Next, a detailed configuration of the image forming unit 12 according to the first embodiment will be described with reference to FIG.

  The image forming unit 12 includes a cylindrical photosensitive drum 30 as an image carrier, and rotates in the arrow direction by a driving force of a motor (not shown). Further, the intermediate transfer belt 14, the contact member 32, the cleaning device 34, the charging roll 36, and the developing device 38 are in contact with the photosensitive surface 30A of the photosensitive drum 30 in order along the rotation direction. Further, a light beam is scanned along the axial direction of the photosensitive drum 30 from the exposure device 40 on the photosensitive surface 30A between the charging roll 36 and the developing device 38.

  The charging roll 36 is applied with a predetermined bias voltage from a power source (not shown), and uniformly charges the abutting photosensitive surface 30A.

  The exposure device 40 uniformly scans the charged photosensitive surface 30A with a light beam based on image data. As a result, the potential of the region scanned by the light beam on the photosensitive surface 30A is lowered to form an electrostatic latent image.

  The developing device 38 includes a developing roll 38 </ b> A that can rotate about a rotation axis parallel to the photosensitive drum 30. The developing roller 38A is applied with a predetermined developing bias voltage from a power source (not shown) to charge the toner to a negative polarity, and rotates in the same direction as the rotation direction of the photosensitive drum 30 to transfer the charged toner to the photosensitive surface 30A. Supply. That is, the developing device 38 rotates the developing roll 38A in the reverse direction with respect to the photosensitive drum 30 at the nip portion that contacts the photosensitive surface 30A. It is increasing.

  A contact point (transfer position) with the intermediate transfer belt 14 is located downstream of the developing device 38 in the rotation direction, and the transfer roll 42 is sandwiched between the photosensitive drum 30 and the intermediate transfer belt 14. Is arranged. A positive transfer voltage having a polarity opposite to that of the toner is applied to the transfer roll 42 from a power source (not shown).

As shown in FIG. 3, the contact member 32 is a brush in which conductive nylon fibers 32B are planted on a rectangular column-shaped conductive base 32A made of metal or the like, and the thickness per brush hair is 2d. (Denier) (15.0 μm), the hair density of the brush is 240 kf / inch ² . A voltage having a negative polarity of the power source 44 is applied to the contact member 32.

  The cleaning device 34 has a rotating brush 34A that is rotatable about a rotation axis parallel to the photosensitive drum 30, and a rotating brush 34A that is in contact with the rotating brush 34A and is parallel to the rotating brush 34A. A recovery roll 34B that is driven and rotated, and a scraper 34C that contacts the peripheral surface of the recovery roll 34B are provided. A large number of brushes are implanted around the rotating brush 34A. The rotating brush 34A is made into a switch unit 54 via a connection line 48, and one of the two power sources of the first plus power source 64 and the second plus power source 66 is selected by the switch unit 54, and a predetermined brush is applied to the surrounding brushes. A voltage is applied. In the present embodiment, as an example, the first plus power source 64 is a DC power source having a voltage V = + 50V, and the second plus power source 66 is a DC power source having a voltage V = + 250V.

  Here, specifications of main members and main electric specifications constituting the image forming unit 12 according to the present embodiment will be described below.

Photosensitive drum 30: Organic photoconductor having a diameter of about 30.0 mm Charging roll 36: Semiconductive roll
DC + AC contact charging system
V _DC = −520v (DC component voltage value)
I _AC = 0.65 mA (AC component current value)
Frequency = 614Hz (AC component voltage waveform)
Exposure apparatus 40: Laser wavelength = 780 nm
Developing roll 38A: Diameter = 16.0 mm
Rotation speed = 208mm / sec
The direction of rotation is opposite to the direction of rotation of the photosensitive drum 30.
Development bias: V _DC = −400 V (DC component voltage value)
V _pp = 1500V (AC component voltage (Peak to Peak))
Frequency = 6 kHz (AC component voltage waveform)
Development system: Two-component development system Development gap (interval between the photosensitive drum 30 and the development roll 38A): about 0.3 mm
Intermediate transfer belt 14: made of polyimide, process speed: 104 mm / second, transfer roll 42: transfer bias + 500V to + 1000V
Transfer roll 26: Transfer bias + 1600V
Note that the photosensitive drum 30 according to the present exemplary embodiment has a discharge start voltage of 450 V at which discharge occurs between other members in contact with the photosensitive drum 30.

  By the way, in the printer 10 according to the present embodiment, an applied voltage control process for controlling the voltage applied to the rotating brush 34A by controlling the switch unit 54 according to the rotational drive of the photosensitive drum 30 is performed. .

  FIG. 4 is a block diagram illustrating a functional configuration of a control system that performs control related to the applied voltage control process in the printer 10.

  As shown in the figure, the printer 10 includes a control unit 50 that controls the operation of each device built in the printer 10 based on input image data and controls the formation of an image on a sheet P, and various types. A storage unit 52 is provided for storing programs and various parameters in advance, and temporarily storing image data indicating an image to be formed.

  The control unit 50 is electrically connected to the storage unit 52 and the switch unit 54. Therefore, the control unit 50 can access the storage unit 52 at any time, and can output a command signal to the switch unit 54 to control the voltage applied to the rotating brush 34A.

  In addition, the control unit 50 has a built-in timer 56 for measuring time.

  Hereinafter, a flow from forming a toner image in the image forming unit 12 to transferring it to the intermediate transfer belt 14 and collecting the transfer residual toner generated on the photosensitive surface 30A after the transfer will be briefly described.

  As shown in FIG. 5, when the photosensitive drum 30 rotates in the direction of the arrow in the drawing, first, the photosensitive surface 30 </ b> A is uniformly charged to a predetermined polarity potential by the charging roll 36. In the present embodiment, a bias voltage obtained by superimposing a DC voltage of −520 V and an AC voltage that generates an AC current of 0.65 mA is applied to the charging roll 36, and the photosensitive surface 30 </ b> A is charged to −500 V, for example. Is done.

  When the photosensitive drum 30 is further rotated, the charged surface of the photosensitive surface 30A is scanned and exposed based on the image data by the exposure device 40, and the potential of the exposed portion of the charged surface is decreased (for example, −200 V). An electrostatic latent image is formed. Thereafter, the toner charged negatively by the developing roll 38A to which a developing bias voltage in which a DC voltage of −400 V and an AC voltage having a peak-to-peak potential difference of 1500 V are superimposed is applied is exposed on the charged surface. By electrically adhering to the portion, the electrostatic latent image is developed (visualized) to form a toner image.

  Then, when the formed toner image passes through the transfer position as the photosensitive drum 30 rotates, the toner image is electrically attracted to the transfer roll 42 to which a transfer voltage of +500 V opposite in polarity to the toner is applied. Then, the image is transferred from the photosensitive drum 30 to the intermediate transfer belt 14.

  However, in the image forming unit 12, the toner transferred to the intermediate transfer belt 14 without being transferred to the intermediate transfer belt 14 or transferred to the intermediate transfer belt 14 on the upstream side is transferred to the downstream photosensitive drum 30. The transfer residual toner that is reversely transferred and remains on the photosensitive drum 30 is generated. The transfer residual toner includes toner having a reverse polarity in which the polarity is reversed to positive by the positive transfer voltage applied to the transfer roll 42 when passing through the transfer position.

  Therefore, in the present embodiment, a voltage of −800 V is applied to the contact member 32 to generate a discharge between the photosensitive drum 30 and the polarity of the residual transfer toner passing therethrough is unified to a negative polarity. The electric potential of the peripheral surface of the photosensitive drum 30 after passing through the contact member 32 becomes approximately −350 V due to discharge from the contact member 32.

  In the cleaning device 34, the rotating brush 34A to which a voltage of +50 V is applied is rotated to attract and collect (clean) the transfer residual toner charged to a negative polarity. The collected transfer residual toner is transferred from the rotating brush 34A to the collecting roll 34B, and is removed and collected by the scraper 34C. The potential difference between the rotating brush 34A and the photosensitive drum 30 is 400V, which is smaller than 450V, which is the discharge start voltage, and no discharge occurs.

  By the way, since the contact member 32 is a brush in which the conductive nylon fiber 15B is implanted, the transfer residual toner is gradually accumulated as the usage time elapses, and when the photosensitive drum 30 starts to rotate. A large amount of transfer residual toner may be discharged from the contact member 32 onto the photoreceptor.

  Therefore, the control unit 50 according to the present embodiment executes an applied voltage control process for controlling the applied voltage to the rotating brush 34A at the start of the rotational driving of the photosensitive drum 30 in order to remove the large amount of transfer residual toner. To do.

  Next, the operation of the printer 10 when the applied voltage control process is executed will be described with reference to FIG. FIG. 6 is a flowchart showing the flow of processing of the applied voltage control processing program executed by the control unit 50 of the printer 10 at this time, and the program is stored in a predetermined area of the storage unit 52 in advance. In addition, here, only control related to one contact member 32 will be described in order to avoid complications, but the control unit 50 performs similar processing on each contact member 32.

  First, in step 100 of FIG. 3, after initializing the timer 56, the timer 56 starts measuring time, thereby measuring an elapsed time t after the photosensitive drum 30 starts to rotate.

  In the next step 102, an instruction signal for instructing switching is output to the switch unit 54 so as to select the second plus power source 66 side. The switch unit 54 electrically connects the rotating brush 34 </ b> A and the second plus power source 66. As a result, as shown in FIG. 7, a voltage of 250 V is applied from the second plus power source 66 to the rotating brush 34A.

  In the next step 104, it is determined whether or not the elapsed time t has passed a predetermined period (for example, 3 seconds). If the determination is affirmative, the process proceeds to step 104. If the determination is negative, the step is performed again. The process proceeds to 102 and waits for a predetermined period of time.

  In step 106, an instruction signal for instructing switching is output to the switch unit 54 so as to select the first plus power source 64 side, and the applied voltage control process is terminated. As a result, a voltage of 50 V is applied from the first plus power source 64 to the rotating brush 34A.

  As described above, according to the present embodiment, the rotating brush 34A is applied with a voltage of 250 V for a predetermined period, so that the adsorption force between the rotating brush 34A and the transfer residual toner is increased. A large amount of transfer residual toner discharged from the contact member 32 at the start of the rotation drive of 30 can be adsorbed and collected.

  Note that, during a predetermined period in which a voltage of 250 V is applied to the rotating brush 34 </ b> A, after the photosensitive drum 30 starts to rotate, the transfer residual toner discharged from the contact member 32 rotates with the rotation of the photosensitive drum 30. It is sufficient that the period of time passes through at least once through 34A, and the number of times of passage of the rotating brush 34A may be obtained by experiments or the like in accordance with the amount of transfer residual toner to be discharged, and the period may be appropriately determined in advance.

  Further, by applying a voltage of 250V to the rotating brush 34A, the potential difference between the rotating brush 34A and the photosensitive drum 30 becomes 600V, and a slight discharge is generated to generate a discharge product, but a discharge is generated. Since the time is limited to a predetermined period, the amount of electricity generated is small and image quality does not deteriorate.

  The printer 10 according to the present embodiment performs the applied voltage control process when the photosensitive drum 30 starts to rotate and performs a sheet passing test on 30,000 sheets of paper P. A large amount of transfer residual toner discharged from the contact member 32 at the start of driving can be sufficiently cleaned, and no white spots have occurred in the image due to the discharge product, which is a concern due to an increase in potential difference.

  As described above, according to the first embodiment, the circumferentially charged image carrier (here, the photosensitive drum 30) is driven to rotate, and a light beam is applied to the circumferential surface of the image carrier. Forming an electrostatic latent image, transferring a toner image developed by attaching toner to the electrostatic latent image onto a recording medium (here, paper P) (here, printer 10) A contact member (here, a contact) which is disposed in contact with the circumferential surface of the image carrier downstream of the toner image transfer position and to which a voltage of a predetermined polarity (here, minus) is applied. The transfer residual toner remaining on the peripheral surface of the image carrier after the transfer is charged to a predetermined polarity by the member 32), and is disposed in contact with the peripheral surface of the image carrier downstream in the circumferential direction from the contact member. The polarity opposite to the predetermined polarity with respect to the potential of the peripheral surface of the image carrier, and Residual toner collecting means (here, the rotating brush 34A) to which a voltage of a predetermined potential difference is applied is adsorbed and collected by the transfer residual toner charged to a predetermined polarity, and the voltage control means (control unit 50). The applied voltage to the residual toner collecting unit is set so that the potential difference between the peripheral surface of the image carrier and the residual toner collecting unit is larger than the predetermined potential difference for a predetermined period from the start of the circumferential driving of the image carrier. Since the control is performed, it is possible to prevent the occurrence of defective cleaning while suppressing the deterioration of the quality of the formed image.

  Further, according to the first embodiment, since the residual toner charging means is a brush at least partly composed of conductive fibers, the transfer residual toner can be charged efficiently.

  Note that the contact member 32 according to the present embodiment needs to be conductive in order to negatively adjust the transfer residual toner to a negative charge. Therefore, as described above, when the brush in which conductive fibers are implanted is used. However, the present invention is not limited to this, and even a brush in which conductive fibers and insulating fibers are mixed woven has conductivity, so that the charge of the transfer residual toner can be adjusted. Alternatively, a brush in which conductive fibers and insulating fibers are mixed may be used.

  Further, the contact member 32 may be provided with an oscillation mechanism that slides in the axial direction in order to make the toner charge adjustment capability uniform in the axial direction.

  In addition, the cleaning device 34 according to the present embodiment includes the rotating brush 34A, the collection roll 34B, and the scraper 34C. However, in the printer 10 with a small amount of residual toner, only the flickering bar is provided. A simple configuration may be adopted.

[Second Embodiment]
In the second embodiment, an example in which a nonwoven fabric is used as the contact member 32 instead of a brush will be described.

  Since the configuration of the printer 10 and the configuration of the control system according to the second embodiment are the same as those in FIGS. 1 and 4, detailed description thereof is omitted here.

  In addition, the image forming unit 12 according to the second embodiment uses a non-woven fabric as the contact member 32, and other configurations are the same as those in FIG.

  As shown in FIG. 8, the contact member 32 according to the second embodiment has a conductive urethane sponge 32C having a thickness of 3 mm attached to a rectangular columnar conductive base 32A made of metal or the like. A nonwoven fabric 32D having a thickness of 500 μm (0.5 mm) is attached on the conductive urethane sponge 32C. The non-woven fabric is literally “a non-woven fabric” and is a sheet formed by laminating conductive fibers obtained by polymerizing conductive polymer polypyrrole on nylon and polyester having a diameter of about 5 μm. As a manufacturing method of a nonwoven fabric, there are a dry nonwoven fabric, a spun band, a wet nonwoven fabric and the like.

  The second plus power source 66 is a DC power source with a voltage V = + 150V.

  In the printer 10 according to the second embodiment, when the photosensitive drum 30 starts to rotate, an application voltage control process is executed by the control unit 50 to start rotating the photosensitive drum 30. During a predetermined period, a voltage is applied from the second plus power source 66 to the rotating brush 34A.

  In the second embodiment, since the non-woven fabric is used as the contact member 32, the amount of transfer residual toner deposited is smaller than that of the brush, and immediately after the photoconductor drum 30 is driven, the contact member 32 moves onto the photoconductor drum 30. The amount of transfer residual toner discharged to the surface is small compared to the brush. Therefore, even if the voltage applied to the rotating brush 34A after starting rotation of the photosensitive drum 30 is + 150V and the potential difference between the photosensitive drum 30 and the rotating brush 34A is 500V, the transfer residual toner is collected. be able to.

  In the printer 10 of this embodiment, when the photosensitive drum 30 starts to rotate using the contact member 32 made of nonwoven fabric, the applied voltage control process is executed to pass 30,000 sheets of paper P. As a result of the test, it is possible to sufficiently clean the transfer residual toner discharged from the contact member 32 when the photosensitive member is driven to the end, and the whiteout of the image due to the discharge product, which is a concern due to the potential difference being increased, has not been obtained. It was outbreak.

  As described above, according to the second embodiment, since the residual toner charging means is a non-woven fabric at least partly composed of conductive fibers, the residual toner when the photosensitive drum 30 starts to rotate. The amount of transfer residual toner discharged from the charging means can be reduced.

  In this embodiment, the case where the potential difference between the photosensitive drum 30 and the rotating brush 34A is set to 500 V has been described. However, the present invention is not limited to this, and the transfer residual toner discharged from the contact member 32 is not limited thereto. The potential difference may be determined as appropriate according to the amount of.

  Moreover, although the case where the nonwoven fabric was used as the contact member 32 was demonstrated in this Embodiment, this invention is not limited to this, What is necessary is just a conductive fixed member, and according to a fixed member. The applied voltage can be determined appropriately.

[Third Embodiment]
In the third embodiment, an example in which the voltage applied during a predetermined period after the rotation of the photosensitive drum 30 is started will be described.

  Since the configuration of the printer 10 according to the third embodiment is the same as that in FIG. 1, a detailed description thereof is omitted here.

  FIG. 9 shows a detailed configuration of the image forming unit 12 according to the third embodiment. In FIG. 9, the same components as those of the image forming unit 12 (FIG. 2) according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted here.

The contact member 32 according to the present embodiment is a brush in which conductive nylon fibers 15B are planted, and the thickness per brush hair is 2d, and the brush hair density is 430 kf / inch ² . . Further, the contact member 32 is connected to the switch unit 56 through the connection line 49, and one of the two negative power sources 68 and 70 is selected by the switch unit 56, and the contact brush 32 is applied to the surrounding brush. A predetermined voltage is applied. In the present embodiment, as an example, the first negative power source 68 is a DC power source having a voltage V = −800V, and the second negative power source 70 is a DC power source having a voltage V = −1000V.

  Further, a voltage is applied to the rotating brush 34A from the first plus power source 64.

  The control unit 50 (see FIG. 4) according to the third embodiment is electrically connected to the switch unit 56 instead of the switch unit 54, and outputs an instruction signal to the switch unit 56 to the contact member 32. The applied voltage can be controlled.

  By the way, since the contact member 32 according to the present embodiment is a brush in which the brush hairs are planted at a higher density than in the first embodiment described above, a large amount of transfer residual toner is accumulated with use, When the photosensitive drum 30 starts to rotate, a large amount of transfer residual toner is discharged from the contact member 32 onto the photosensitive member.

  The transfer residual toner discharged from the contact member 32 includes a positive polarity in addition to a negative polarity, but is charged to a negative polarity by a negative voltage applied from the contact member 32. .

  However, with the brush in which the conductive nylon fibers 15B are planted at a high density as in the present embodiment, a large amount of transfer residual toner is discharged, and thus all transfer residual toner cannot be charged to a negative polarity. In some cases, a positive polarity may remain. For example, in the configuration of the image forming unit 12 according to the present embodiment, the ratio of the positive polarity of the transfer residual toner discharged from the contact member 32 immediately after the rotation of the photosensitive drum 30 is 15 when the applied voltage is −800V. It was 3% at −1000 V (measured with E-SPART ANALYZER manufactured by Hosokawa Micron).

  Therefore, the control unit 50 according to the present embodiment starts the rotation driving of the photosensitive drum 30 in order to negatively charge a large amount of transfer residual toner discharged with the start of the rotation driving of the photosensitive drum 30. At this time, an applied voltage control process for controlling the applied voltage to the contact member 32 is executed.

  Next, the operation of the printer 10 when the applied voltage control process is executed will be described with reference to FIG. Note that the same reference numerals are given to the same processing as the applied voltage control processing (FIG. 6) according to the first embodiment in FIG. 10, and description thereof is omitted here.

  In step 112, an instruction signal instructing switching is output to the switch unit 56 so as to connect the contact member 32 and the second negative power source 70, and the applied voltage control process is terminated. As a result, a voltage of −1000 V is applied to the contact member 32 from the second negative power source 70.

  In step 116, an instruction signal for instructing switching is output so that the contact member 32 and the first negative power source 68 are connected to the switch unit 56. As a result, a voltage of −800 V is applied to the rotating brush 34A from the first negative power source 68.

  Thus, according to the present embodiment, as shown in FIG. 11, the contact member 32 is applied with a voltage of −1000 V from the second negative power source 70 for a predetermined period. A large amount of transfer residual toner discharged from the toner can be negatively charged.

  The photosensitive surface 30 </ b> A that has passed through the contact member 32 is charged to −550 V by the voltage from the contact member 32. Therefore, in the third embodiment, even if the voltage applied to the rotating brush 34A is not changed, the potential difference between the rotating brush 34A and the photosensitive surface 30A is increased, and the adsorption force with the transfer residual toner is increased. A large amount of transfer residual toner discharged from the member 32 can be adsorbed and collected.

  In addition, by setting the applied voltage to the contact member 32 to −1000 V, the potential difference from the photosensitive drum 30 increases, and discharge occurs to generate a discharge product. The period for applying −1000 V is a predetermined period. Therefore, the amount of electricity generated is small and the image quality is not deteriorated.

  In the printer 10 of the present embodiment, when the photosensitive drum 30 is driven to rotate, the applied voltage control process is executed, and a sheet passing test for 30,000 sheets of paper P is performed. A large amount of transfer residual toner discharged from the contact member 32 can be sufficiently cleaned, and no white spots have occurred in the image due to a discharge product which is a concern due to an increase in potential difference.

  As described above, according to the third embodiment, the voltage control means controls so that the voltage value of the voltage applied to the contact member is increased for a predetermined period, so that a large amount is discharged. The transfer residual toner can be charged to a predetermined polarity.

  In the present embodiment, the case where only the voltage applied to the contact member 32 is changed has been described. However, the present invention is not limited to this and is described above together with the voltage applied to the contact member 32. As shown in the first embodiment, the voltage applied to the rotating brush 34A may be changed. Also in this case, the same effect as in the present embodiment can be obtained.

[Fourth Embodiment]
In the fourth embodiment, an example in which the potential of the contact member 32 is set to the ground level and the transfer residual toner is collected by applying an AC voltage to the rotating brush 34A will be described.

  Since the configuration of the printer 10 according to the fourth embodiment is the same as that shown in FIG. 1, detailed description thereof is omitted here.

  FIG. 12 shows a detailed configuration of the image forming unit 12 according to the fourth embodiment. The same components as those of the image forming unit 12 (FIG. 2) according to the first embodiment in FIG. 12 are denoted by the same reference numerals, and description thereof is omitted here.

  The contact member 32 according to the present embodiment is grounded via the connection line 49, and the potential is set to the ground level (0 V).

  Further, the rotating brush 34A of the cleaning device 34 is connected to the switch unit 54 via the connection line 48, and one of the two power sources of the first power source 72 and the second power source 74 is selected by the switch unit 54, A predetermined voltage is applied to the brush. As an example in the present embodiment, the first power source 72 is a power source in which a DC voltage of −100 V and an AC voltage with a peak-to-peak potential difference of 800 V and a frequency = 3.2 kHz are superimposed. The dual power source 74 is a power source in which a DC voltage of −100 V and an AC voltage having a peak-to-peak potential difference of 1200 V and a frequency = 3.2 kHz are superimposed.

  Hereinafter, a flow until the transfer residual toner generated on the photosensitive surface 30A after the transfer is collected will be briefly described.

  In the present embodiment, the potential of the contact member 32 is set to the ground level. Therefore, the polarity of the transfer residual toner passing therethrough does not change, and the peripheral surface of the photosensitive drum 30 after passing through the contact member 32 is discharged to about −100V.

  In the cleaning device 34, an AC voltage having a peak-to-peak potential difference of about 800V is applied to the rotary brush 34A from the first power source 72, and the transfer residual toner having negative and positive polarities is applied to the rotary brush 34A. Are adsorbed together and recovered.

  However, the contact member 32 according to the present embodiment gradually accumulates transfer residual toner with use, and a large amount of transfer residual toner is transferred from the contact member 32 when the photosensitive drum 30 starts to rotate. May be discharged above.

  Therefore, the control unit 50 according to the present embodiment controls applied voltage to the rotating brush 34A when the photosensitive drum 30 starts to rotate in order to remove the large amount of transfer residual toner. Execute the process.

  Next, the operation of the printer 10 when the applied voltage control process is executed will be described with reference to FIG. The same processes as those in the applied voltage control process (FIG. 6) according to the first embodiment in FIG. 13 are denoted by the same reference numerals, and description thereof is omitted here.

  In the next step 122, an instruction signal for instructing switching is output to the switch unit 54 so as to select the second power source 74 side. Thereby, the switch unit 54 electrically connects the contact member 32 and the second power source 74. As a result, an AC voltage having a peak-to-peak potential difference of 1200 V is applied to the rotating brush 34A from the second power source 74 with -100V as the center.

  In step 126, an instruction signal for instructing switching is output to the switch unit 54 so as to select the first power source 72 side, and the applied voltage control process is terminated. As a result, an AC voltage having a peak-to-peak potential difference of 800V is applied to the rotating brush 34A from the first power source 72 with -100V as the center.

  Thus, according to the present embodiment, the cleaning device 34 has a positive and negative potential difference of 600V (peak-to-peak potential difference of 1200V) centered on -100V on the rotating brush 34A for a predetermined period. When the voltage is applied, the adsorption force between the rotating brush 34A and the transfer residual toner is increased, and therefore, a large amount of transfer residual toner discharged from the contact member 32 is adsorbed when the photosensitive drum 30 starts to rotate. Can be recovered.

  Further, when the potential difference between the rotating brush 34A and the photosensitive drum 30 is 600V, a slight discharge is generated and a discharge product is generated. However, since the discharge generation period is limited to a predetermined period, the electric product The amount of generated image is small and image quality does not deteriorate.

  In the printer 10 of the present embodiment, when the photosensitive drum 30 is driven to rotate, the applied voltage control process is executed, and a sheet passing test for 30,000 sheets of paper P is performed. A large amount of transfer residual toner discharged from the contact member 32 can be sufficiently cleaned, and no white spots have occurred in the image due to a discharge product which is a concern due to an increase in potential difference.

  As described above, according to the fourth embodiment, the contact member is connected to the grounded wiring (in this case, the connection line 49), so that the potential is set to the ground level and the peripheral surface of the image carrier is removed. The residual toner collecting means is applied with an AC voltage whose potential difference from the center is a predetermined potential difference, and the voltage control means is configured to maintain the residual toner for a predetermined period. The applied voltage to the residual toner collecting means is controlled so that the potential difference from the center of the AC voltage applied to the collecting means is larger than the predetermined potential difference, so that the deterioration of the quality of the formed image is suppressed. The occurrence of defective cleaning can be prevented.

  In the first to fourth embodiments, the case where the photosensitive drum is cylindrical has been described. However, the present embodiment is not limited to this, and for example, wound around a plurality of rolls. It is good also as an endless belt hung. Also in this case, the same effect as in the present embodiment can be obtained.

  In the applied voltage control processing according to the first, third, and fourth embodiments, the case where the voltage applied to the contact member 32 or the rotating brush 34A is changed by providing a switch and switching the power source will be described. However, the present invention is not limited to this, and when the power supply can change the applied voltage, the applied voltage may be changed by controlling the power supply. Also in this case, the same effect as in the present embodiment can be obtained.

  Further, the configuration of the printer 10 described in this embodiment (see FIG. 1) and the configuration of the image forming unit (see FIGS. 2, 5, 7, 9, 11, and 12) are examples. Needless to say, modifications can be made as appropriate without departing from the scope of the present invention.

  The applied voltage control processing (see FIGS. 6, 10, and 13) described in the first, third, and fourth embodiments is also an example, and can be changed as appropriate without departing from the gist of the present invention. It goes without saying that it is possible.

1 is a diagram illustrating an overall configuration of a printer according to an embodiment. FIG. 2 is a diagram illustrating a detailed configuration of an image forming unit according to the first embodiment. It is a figure which shows the detailed structure of the contact member which concerns on 1st Embodiment. 2 is a block diagram illustrating a configuration of a control system of the printer according to the first embodiment. FIG. FIG. 5 is a diagram illustrating a toner flow of the image forming unit during image formation in the image forming unit according to the first embodiment. It is a flowchart which shows the flow of the applied voltage control process which concerns on 1st Embodiment. FIG. 5 is a diagram illustrating a toner flow at the start of rotation driving in the image forming unit according to the first embodiment. It is a figure which shows the detailed structure of the contact member which concerns on 2nd Embodiment. It is a figure which shows the detailed structure of the image forming unit which concerns on 3rd Embodiment. It is a flowchart which shows the flow of the applied voltage control process which concerns on 3rd Embodiment. FIG. 10 is a diagram illustrating a toner flow when rotation driving is started in an image forming unit according to a third embodiment. It is a figure which shows the detailed structure of the image forming unit which concerns on 4th Embodiment. It is a flowchart which shows the flow of the applied voltage control process which concerns on 4th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Printer 30 Photosensitive drum 32 Contact member 34A Rotary brush 50 Control part

Claims (4)

An image carrier having a uniformly charged peripheral surface is driven to circulate, a light beam is applied to the peripheral surface of the image carrier to form an electrostatic latent image, and toner is attached to the electrostatic latent image. An image forming apparatus for transferring a developed toner image to a recording medium,
The toner image is placed in contact with the circumferential surface of the image carrier downstream in the circumferential direction from the transfer position of the toner image, and a voltage having a predetermined polarity is applied, and remains on the circumferential surface of the image carrier after the transfer. A contact member for charging the transfer residual toner to the predetermined polarity;
The contact member is disposed in contact with the peripheral surface of the image carrier on the downstream side in the circumferential direction, and has a predetermined potential difference with a polarity opposite to the predetermined polarity with respect to the potential of the peripheral surface of the image carrier. A residual toner collecting means for attracting and collecting the transfer residual toner charged with a predetermined polarity and applied with a voltage;
The transfer residual toner that accumulates on the contact member with the passage of time of use and is discharged from the contact member onto the image carrier when the rotation of the image carrier starts is started to rotate around the image carrier. From the time until the toner passes through the residual toner collecting means as the image carrier rotates, at least a predetermined number of times according to the amount of the transferred residual toner discharged. Voltage control means for controlling a voltage applied to the residual toner collecting means so that a potential difference between the peripheral surface of the body and the residual toner collecting means is larger than the predetermined potential difference;
An image forming apparatus. An image carrier having a uniformly charged peripheral surface is driven to circulate, a light beam is applied to the peripheral surface of the image carrier to form an electrostatic latent image, and toner is attached to the electrostatic latent image. An image forming apparatus for transferring a developed toner image to a recording medium,
The toner image is placed in contact with the circumferential surface of the image carrier downstream in the circumferential direction from the transfer position of the toner image, and a voltage having a predetermined polarity is applied, and remains on the circumferential surface of the image carrier after the transfer. A contact member for charging the transfer residual toner to the predetermined polarity;
The contact member is disposed in contact with the peripheral surface of the image carrier on the downstream side in the circumferential direction, and has a predetermined potential difference with a polarity opposite to the predetermined polarity with respect to the potential of the peripheral surface of the image carrier. A residual toner collecting means for attracting and collecting the transfer residual toner charged with a predetermined polarity and applied with a voltage;
The transfer residual toner that accumulates on the contact member with the passage of time of use and is discharged from the contact member onto the image carrier when the rotation of the image carrier starts is started to rotate around the image carrier. The contact member during a period from the time until it passes through the residual toner collecting means with the rotation of the image carrier at least a predetermined number of times according to the amount of the transferred residual toner discharged Voltage control means for controlling the voltage applied to the contact member such that the voltage value of the voltage applied to the contact member is greater than the voltage of the predetermined polarity;
An image forming apparatus. An image carrier having a uniformly charged peripheral surface is driven to circulate, a light beam is applied to the peripheral surface of the image carrier to form an electrostatic latent image, and toner is attached to the electrostatic latent image. An image forming apparatus for transferring a developed toner image to a recording medium,
The toner image is placed in contact with the circumferential surface of the image carrier downstream in the circumferential direction from the transfer position of the toner image, and a voltage having a predetermined polarity is applied, and remains on the circumferential surface of the image carrier after the transfer. A contact member for charging the transfer residual toner to the predetermined polarity;
The contact member is disposed in contact with the peripheral surface of the image carrier on the downstream side in the circumferential direction, and has a predetermined potential difference with a polarity opposite to the predetermined polarity with respect to the potential of the peripheral surface of the image carrier. A residual toner collecting means for attracting and collecting the transfer residual toner charged with a predetermined polarity and applied with a voltage;
The transfer residual toner that accumulates on the contact member with the passage of time of use and is discharged from the contact member onto the image carrier when the rotation of the image carrier starts is started to rotate around the image carrier. From the time until the toner passes through the residual toner collecting means as the image carrier rotates, at least a predetermined number of times according to the amount of the transferred residual toner discharged. The voltage applied to the residual toner collecting means is controlled so that the potential difference between the peripheral surface of the body and the residual toner collecting means is larger than the predetermined potential difference, and the voltage applied to the contact member Voltage control means for controlling the voltage applied to the contact member such that the value is greater than the voltage of the predetermined polarity;
An image forming apparatus. An image carrier having a uniformly charged peripheral surface is driven to circulate, a light beam is applied to the peripheral surface of the image carrier to form an electrostatic latent image, and toner is attached to the electrostatic latent image. An image forming apparatus for transferring a developed toner image to a recording medium,
The electric potential is set to the ground level by being arranged in contact with the peripheral surface of the image carrier at the downstream side in the circumferential direction from the transfer position of the toner image and connected to a grounded wiring, so that the peripheral surface of the image carrier. A contact member for removing the charge to a predetermined potential level;
An AC voltage is applied so that a potential difference from the center is a predetermined potential difference centered on the predetermined potential level, and is arranged in contact with the peripheral surface of the image carrier downstream of the contact member in the circumferential direction. A residual toner collecting means for adsorbing and collecting the transfer residual toner charged in polarity;
The transfer residual toner that accumulates on the contact member with the passage of time of use and is discharged from the contact member onto the image carrier when the rotation of the image carrier starts is started to rotate around the image carrier. From the time until the toner passes through the residual toner collecting means according to the rotation of the image carrier at least once determined in accordance with the amount of the transferred residual toner discharged. Voltage control means for controlling an applied voltage to the residual toner collecting means so that a potential difference from the center of the AC voltage applied to the collecting means is larger than the predetermined potential difference;
An image forming apparatus.

Images